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02-23-2012, 03:27 PM #1Registered User
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Avalanche airbags, how effective are they really?
Last week we tragically had an avalanche which killed two men (leaving behind a total of 7 children) who were touring in Northern Norway. It was a large avalanche, 2-300m wide, 0.3-1.5m thick at the top and it travelled 650m. One of the deceased had an airbag which was deployed but he was buried at 1-1.5m depth. There will be a full report on this by the authorities when they have all the facts. In Norwegian:
http://translate.google.com/translat...2FEnormt-skred
I understand airbags isn’t a guarantee against beeing buried but it got me thinking. I am, like most people, considering buying one of these packs and I’m wondering which one and should I get one at all? ABS has statistics which state that 97% survive. When I see the number 97% I almost automaticly think ”everyone”. It chocked me a bit when I heard he had a deployed airbag.
http://www.abs-airbag.com/
http://www.slf.ch/
I don’t understand german but here’s a guy who obviously doesn’t fully trust all the facts stated by ABS-airbags:
Do you know of other accidents where the victims have deployed their airbags and still been totally buried, balloons and all?
Last year a guy in my local skiarea had one of his balloons in his ABS-pack punctured when he was caught by an avalanche. Since then I have always thought of the ABS-pack to be safer then the rest because of the redundancy of 2 balloons. But after watching the youtube video above I may be prone to thinking that the snowpulse system would be better at keeping your head above the snow. I don’t understand why they can’t divide the balloon into two so that half would stay inflated even if it’s punctured.
A lot of people are starting to wear theese bags now. I would like to hear all stories of actual avalanches with victims who had airbags. What’s your experience?
Did they stay on top and do you believe it was because of the airbag?
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02-23-2012, 03:53 PM #2
redunancy doesn't mean much IMO w/ regards to puncturing a airbag. If one get's punctured - the remaining one will not likely be big enough to keep you afloat.
It's the brazil nut effect that is keeping you ontop - which doesn't mean that you'll necessary stay on top the whole time.
Avy-ing through trees is going to be a disaster almost any way you slice it.
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02-23-2012, 05:31 PM #3
Size matters too. That sounds like a pretty big slide, so chances of a burial are going to go up. Other then not getting caught in a slide airbags are still your best bet at surviving a slide, but there is no guarantee.
I agree it is a constitutional right for Americans to be assholes...its just too bad that so many take the opportunity...iscariot
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02-23-2012, 05:38 PM #4
If you look at the multiple fatality avy at steven's pass...of the 5 (i believe) people who were caught in the slide the only one that survived was Elyse Saugstad, who was the only one to have and deploy her airbag. When interviewed she gives full credit to the airbag being the reason she was only partially buried, and thus surviving the avy.
Sounds like a pretty good case of them being extremely effective.Magic Mountain Freeride Team...bringing your grom's game to the next level.
The only ski you'll ever need...http://worthskis.com/skis/the-magic/
"Errare Humanum Est"
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02-23-2012, 05:43 PM #5
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02-23-2012, 05:55 PM #6
there have been lots of tests with avys large and small, using mannequins with and without ABS
ABS always does better in those tests, but every now and then one gets buried.
Terrain, snow texture, size, etc. all have an effect on flotation.
Universally it is agreed they work.
What I worry about is what it does to the heuristics.
will more skiers die with ABS since they feel protected and take more risks??
It has been said that with a beacon, you should still ski as if you have none.
burial is only part of your battle. Trauma (even without trees) can do you in.Kill all the telemarkers
But they’ll put us in jail if we kill all the telemarkers
Telemarketers! Kill the telemarketers!
Oh we can do that. We don’t even need a reason
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02-23-2012, 06:54 PM #7
This. If people start taking bigger risks because they have a airbag, it will negate the benefit of the bag in the first place.
Also worth noting that a lot of the tests(both company R&D and actual usage in a slide) that resulted in the statistics these companies claim were carried out in Europe and BC, where more of the terrain is above treeline. In most areas in the US we are either below the tree line or a slide could carry us into the tree line, resulting in punctured airbags and more deaths due to trauma then in other regions.
But if you can have an ABS on without letting it changing your backcountry habits, it's a great thing.
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02-23-2012, 07:51 PM #8
^^^ This. It should give you pause that someone was wearing an airbag and still did not make it. This comment is in NO way related to who specifically has or has not survived because those instances are specific and I know nothing about them, but I have like others been very worried that more and more people will think they need less training, knowlege, and facility with the basic tools of the avalanche trade because an airbag saves you "97% of the time".
On the statistic itself, this is likely an incredibly misleading use of numbers. If you flipped a coin 5 times, and it came up heads 4 of those 5 times, would you try to sell me a coin as one that comes up heads 80% of the time? I highly doubt the 97% number is statistically significant (in statistics parlance), meaning, the low number of observations means using a statisic like this meaningless. There are also a lot of qualitative factors affecting the statistic: was the slide someone survived with an airbag likely to bury you if you were not wearing the airbag? This is impossible to know, calling into question to legitimacy of the 97% number (or any number), no matter how many observations are obtained.
All of this is not to say this isn't a good piece of safety equipment; it has clearly helped people and I am certainly inclined to carry one. However, this is not a safety net that can replace anything else. The fake 97% number is irresponsible because people actually take it at face value.
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02-23-2012, 08:18 PM #9
At least one company (ABS i think) who purposely started slides with dummies outfitted with airbags in the slidepath also had dummies without airbags getting caught as well for a control group. While the number of times they did this is probably not statistically relevant it shows they were trying to be as accurate as possible.
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02-23-2012, 08:23 PM #10Gel-powered Tech bindings
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The relatively recent switch to the singular 97% figure at the ABS website is somewhat surprising (at least to me) because through at least the 2009-10 season ABS was publishing (and periodically updating) a very detailed database of every single ABS in-the-field deployment ... both actual and attempted, as well as successful (in terms of life or death) and otherwise.
I still have the file, so that and some other non-ABS databases will be the basis for a possible article in the final issue of TAR this season.Mo' skimo here: NE Rando Race Series
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02-24-2012, 12:08 AM #11
I've worn an ABS bag for three years now and wondered how it might effect my habits mindset as well. Let me tell you...it doesn't. I have never taken an additional risk with because the thought of having an ABS bag on my back might be a ticket to safety. Think of it this way. If you're looking down a slope with the potential to avalanche, do you still want to drop in even though you know you have something that "might" save you?
I didn't think so. My bc habits haven't changed one bit since wearing an ABS. It's just nice to know that if the shit does hit the fan, I have one more hope to survive beyond being unburied by my friends.
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02-24-2012, 12:49 AM #12
Does it change the order in which you ski? The reason I ask is because I've been in an ABS for 3 years as well and a few times I've found myself saying internally "If we're wrong in our assessment of this slope and it did go before I'm safe - at least I have the ABS and the other guys don't have it" so I go first.
I don't believe it's ever changed my mind on a slope I've skied on - I tend to be one of the more cautious of my groups or at least the more vocal - but I honestly wonder if I'd know if it was changing my mindset?
I've argued w/ a number of friends and partners who think it's setting you up for getting into a looser set of habits - but I'm still of the belief that having an extra few pounds on my back is worth the last thread of hope if all else fails.
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02-24-2012, 12:52 AM #13
There are a lot of factors that will determine how well the bag keeps someone afloat, or doesn't. If the ride is short the bag won't have much time to pull you to the surface (gotta shake the can of nuts a lot to bring the big nuts to the top). If someone is caught under slabs and the snow really isn't churning much, the bag can't really do it's thing. Or if the chunks of slab are larger than the person w/bag, the big chunks will stay on top. If the person is low on the hillside and the avi dumps on top of them and then halts, they just get buried.
So yeah, for best airbag results the snow is probably soft and fluffy and churns a lot, and is a long ride above treeline. Unfortunately that's exactly not the norm in the lower 48 states, but every little bit helps. I've got a MR Blackjack on order.
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02-24-2012, 01:12 AM #14
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02-24-2012, 01:33 AM #15simen@downskis.com DOWN SKIS
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02-24-2012, 02:45 AM #16Registered User
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What you are getting at are confidence intervals. As you say, if you do a small number of tests to find a percentage of success then you cannot legitimately say that you would find the same percentage in a much larger population. However, it is possible to calculate the range in which the true value is likley to fall (with 95% confidence). This range is called the confidence limit or confidence interval.
In the 97% success rate scenario for airbags, if 33 samples were tested (implied minimum to get 97% figure) then we could say with 95% confidence that the actual figure of success in a much larger population would be in the range of 84.7%-99.5% survival (note it could be better or worse than the tested figure).
As the number of tests goes up then the range narrows in so...
If they tested 50 cases then the range would be 88.0% - 99.3%
If they tested 75 cases then the range would be 90.3% - 99.1%
If they tested 100 cases then the range would be 91.5% - 99.0%
There are a couple of slightly different methods for calculating this which produce different (but not wildly different) numbers. If anyone knows the actual numbers of times that airbags have been triggered and the number of times that they have been successful vs resulted in death then I can calculate the true lower 95% confidence limit, but based on the assumption that they have done at least 30 then the success rate is still pretty convincing.Last edited by gritter; 02-24-2012 at 02:57 AM.
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02-24-2012, 03:15 AM #17Registered User
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This is a good discussion. I still believe it works but it would be nice to see more thorough research and more cases.
By the way ABS states they have 262 cases analyzed by SLF Swiss Avalanche Institute in Davos. I believe these guys are very serious, I've briefly been there myself to look at their operations. Probably the leading avalanche center in Europe.
http://abs-airbag.de/en/abs-system/t...al-principles/
It just appears that now everyone is taking it for granted that it just works. I would also like to hear about the cases when it didn't work perfectly.
Here are a few good videos of when it worked:
Here's a test when the dummy without the airbag did it better then the one with:
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02-24-2012, 03:29 AM #18Registered User
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^^^ 262 cases with 97% success rate would put the likley success rate in the larger population between 94.2% and 98.5%
That is pretty good.
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02-24-2012, 05:35 AM #19
This video was done by Mr. Fournier, inventor and producer of the avalanche ball and part of a website that was an anti-ABS-campaign.
He was ordered by court in 2010 to stop distributing this misinformation. (edit: although I think, in certain ways he had a point. The -lets say: very optimistic use of statistics by ABS for their commercial campaigns is at least morally wrong in my eyes)
The whole procedure was accompanied by vivid discussions in the german websites freeskiers.net and powderguide.com -for those of you understanding german and interested, I can provide links, if wanted.
This video is part of a german TV show on "popular science" and a single incident, that was picked out by the very same person involved above and commented.
Some discussion has been going on on the eligibility of dummy tests in avalanches in regard of final bury position, as dummies are likely not very well simulating human body movements in this situation. (Plus that humans in this situation are unlikely to be inactive)
However, here's a more complete study of test avalanches with dummies by the mentioned SLF Swiss Avalanche Institute (of course, in german... ):
http://www.slf.ch/praevention/verhal...ier_Harvey.pdf
In this study, they tested eight (later 7 because one was destroyed) dummies in four avalanches equipped with nothing, avalanche ball, ABS or snowpulse airbags. Not big numbers, of course...
There are several interesting things mentioned:
- there was no clear influence of the device on the burial position of the dummies
- airbag systems significantly reduced burial depth (best shown in Fig.3 - burial depth of breathway openings (blue bars) and mean +/- 95% confidence interval as calculated by 2000 bootstrap simulations (red lines))
- according to hints or facts that would speed up rescue, they used a point system (Tab.3), where they gave 1 point each for device/body part visible from distance; head visible; or beathways 10cm or less buried. Airbag systems were performing significantly better, while the avalanche ball is just marginally better than nothing
- regarding head trauma: no clear results, although the dummies with the ABS recorded slightly higher forces on the head than ball/nothing dummies, while the snowpulse system reduced these forces. Higher forces with the ABS are possibly attributed to higher position in the flowing avalanche, which is the faster & more turbulent flowing zone within the slide, from which the snowpulse might protect. Forces are generally high, which is not surprising giving the experiments' design with an avalanche hitting from above.
The high forces let often to an upshift of the backback on the dummy bodies resulting in the hip belt being directly below the chin. Although the leg loops are practically never used by skiers, their usage seems advisable
This sounds rather pro-Airbag.
The SLF-statistics said in 2009, that in 180 cases with deployed ABS airbag, 177 persons survived. In the very same accidents 41 persons without airbag were involved, of which 20 were completely buried. 13 of those deceased.
I don't really like this statement so much, as it doesn't tell, how many of the airbag carriers were burried/completely burried and I would like to see it reduced to the cases, where both ABS and non-airbag carriers were involved, but it tells a strong story anyway.
disclaimer: I am not in any way involved with any of these products or companies, just interested in the topicLast edited by Knut; 02-24-2012 at 06:59 AM.
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02-24-2012, 06:53 AM #20Registered User
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Excellent info, thanks Knut
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02-24-2012, 07:37 AM #21Registered User
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So those stats suggest that the chances of survival are as follows:
Nominally with an airbag: 98% vs without 68%.
The number of incidents recorded with an airbag gives a lower confidence limit of 95% which is pretty good.
The number of incidents without an airbag (in this example) only give a lower confidence interval of 53%, so we could use a few more data points here.
Does anyone have more data on the survival rate without airbags for comparison
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02-24-2012, 12:38 PM #22
I have no doubt this is very true for somebody like you with large amounts of experience. I have no doubt you can read conditions better then most. The worry is with the less experienced user who just doesn't have a good ability to read conditions. They may look at a slope and think "well it seems safe, but I am not really sure". I have a pack so I will go ahead and drop. This can also be said for beacons and avalungs as well, so I am not dissing airbags. Especially when people read 97% stats, it is like what the hell, I won't die even if it slides. Which is an obviously bad way to think about it, but with all the knuckleheads heading into the BC these days it is a very real concern.
I agree it is a constitutional right for Americans to be assholes...its just too bad that so many take the opportunity...iscariot
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02-24-2012, 01:24 PM #23
It's all just conjecture until we have some serious #'s to backup an argument like that. Clearly guys with substantial backcountry training are getting caught - now the question is what % of the skier caused avalanches are set off by people with substantial training and years of experience versus less experience but a more keyed up mind that they're in a potentially life threatening environment.
I can tell you from my rock climbing background, that it's way more common to hear about guys with a wealth of experience making judgement errors. They get relaxed because they have done things hundreds, thousands of times. The newbs are still triple checking knots and checking their partners belay devices.
Again, it's baseless opinion without real #'s - but it's interesting to discuss.Last edited by Poop~Ghost; 02-24-2012 at 01:55 PM.
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02-24-2012, 01:42 PM #24
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02-24-2012, 01:56 PM #25
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